Worldbuilding Best Practices: Exception-Based is Best

When it comes to world-building, I find that best practices follow the Exception-Based Design principle. You start with the real world, and then you start making exceptions to it until you iterate your way into what you want. You wouldn't think to be the norm, but I dare you to run to your shelf and start analyzing the settings of your games and stories. Even something very far out there will be built upon the real world as a foundation, and then iterated outward into the final form you receive.

There's a reason for doing it. That reason is obvious as a brick to the face when you think it through: it gives you a reliable fallback for when your fictive postulates don't cover a situation. That's why this is "exception-based"; you use the real world to determine results when fictional elements cannot or do not handle it.

Let's consider an example, taken from one of my own gaming campaign settings:

• This is a D&D setting, using the classic Basic D&D (Mentzer) ruleset. That right there imposes some unstated postulates.
  
• Non-humans exist, but are not available as playable characters.
  
• Gunpowder works, but the technology is not well-developed yet. Firearms are smoothbore flicklock muskets and cannon using black powder.
  
• Magic exists, but those who use it don't truly comprehend what this power is or how it truly works. (This knowledge is, effectively, a form of treasure.)
  
• Player-characters come from a not-Europe that just concluded a not-30 Years War, and your character was on the losing side. This is your way out, as a colonist to a land heretofore unknown.
  

So far, not that odd, right?

Look, it's this simple. When I don't know what to do, I look at the real historical parallel and apply that as best I can to the matter. That's why I stick with exception-based world-building design. It's the same for my fiction, no matter how fantastic it may be. It's classic--Homer, Tolkien, Howard, and more went this way over the ages--and it works. That's why it's a Best Practice.